1. Field of the Invention
The present invention relates to a portable computer, and more particularly, to a portable computer mounted with a planar inverted F antenna.
2. Description of the Related Art
Generally, an antenna has a great effect on an efficiency of a wireless local area network (wireless LAN or WLAN), and has different operation characteristics according to various conditions, such as a shape, installation position, and installation method. Wireless LAN antennas are classified into internal antennas and external antennas. Internal antennas have excellent properties for portability and use, compared with external antennas. Due to theses advantages, demand for internal antennas has steadily increased. A representative antenna of internal antennas is a planar inverted F antenna.
A planar inverted F antenna (PIFA) used in a conventional portable computer, as shown in FIG. 1, comprises: a ground plane 2; a radiator 4 connected to the ground plane 2; and a feeding part 6 positioned on the radiator 4 and connected to an antenna cable. If a gap between the ground plane 2 and the radiator 4, the length of the radiator 4, and the position of the feeding part 6 are adjusted, the planar inverted F antenna with the above configuration can be adjusted to operate in an intended frequency band. This adjustment is called a tuning adjustment.
But the planar inverted F antenna with the above configuration can operate in only one frequency band, and therefore has difficulty in receiving various frequency bands. For example, a wireless LAN antenna used in a 2.4 GHz frequency band can operate in only the 2.4 GHz frequency band, and does not operate normally in other frequency bands.
Thus, to solve the problem, additional antennas may be installed, but the additional installation causes various problems, such as further crowding an already limited installation space, a need for a switching method, and a cost of the additional antennas.
Recently, a multi-band antenna capable of operating in a plurality of frequency bands has been produced. The installation structure of the recent multi-band antenna, however, is not only complex, but also a feeding point thereof connected to an antenna cable is inappropriate. As a result, the recent multi-band antenna can operate in dual bands, but has difficulty in operating in more than two bands.